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The Bad Astronomer writes "As much as 90% of previously hidden galaxies in the distant Universe have been found by astronomers using the Very Large Telescope in Chile. Previous surveys had looked for distant (10 billion light years away) galaxies by searching in a wavelength of ultraviolet light emitted by hydrogen atoms — distant young galaxies should be blasting out this light, but very few were detected. The problem is that the ultraviolet light never gets out of the galaxies, so we never see them. In this new study, astronomers searched a different wavelength emitted by hydrogen, and voila, ten times as many galaxies could be seen, meaning 90% of them had been missed before."

If one of the theories concerning the universe holds true about the size and how it works, looking at one point can cause visual feedback.

The theory is that if you go straight with a velocity with no force ever effecting you you would return to your previous point eventually. In short the universe is curved into itself and like on a planet traveling in 1 direction on the planet returns you to your starting point.

If you look at one point in the universe I would not be surprised if you saw galaxies and objec

A quote from the summary, which should appear directly above the comments in case you are not familiar with slashdot, is:

and voila, ten times as many galaxies could be seen

.

X is the previous amount, and 10x as the new amount of galaxies.

So simple math gives you X + YX = 10XX(1+Y)=10x(1+Y)=10Y=9

So we see a 10-fold total galaxies, which is 9-fold improvement. Or to put it another way, the new 100% is 10 times the previous amount, which must have been 10%, leaving 90% more.

You're reading it as "90% of the universe found", from the headline, which is an attempt, although a poor one, at conveying the increase in observable galaxies. It is correct if you assume that we found 90% of the now-current estimate of the number of galaxies, in other words insert the word "known" in the title somewhere. Choosing not to even read the summary has left you understandably confused, and I'm glad that I was able to help. At the same time, I'm concerned that the other replies did not draw your attention to this. But I was able to post an accurate reply while maintaining an air of disdain and condescension, so that makes me feel good about myself. Thank you for affording me the opportunity, and welcome aboard.

More likely, a huge intellectual battle will break out among humankind, between the Dark Matter proponents and the Dark Matter deniers. Auditoriums full of angry people will hurl insults back and forth at each other, news stations will interview various scientific experts and political commentators in an effort to boost ratings, deniers will accuse the proponents of wanting to destroy the free-market universe and enslave humankind in some kind of subatomic socialism, while proponents will accuse the deniers of being selfish and greedy, willing to gamble the heat death of the entire universe just so they can run their colliders a little longer.

Absolutely wrong. TFA even states this means nothing for dark matter, we knew that these galaxies were out there, we just hadn't spotted them yet. Besides, we've seen dark matter much closer to home. When galaxies collide, the gas pressure stops the regular matter, while the dark matter keeps moving along at the same speed. The dark matter has mass, so it creates a gravatic lens. We have seen these lenses, with no visible matter to create them, when galaxies collide.

I knew about the fudge factor we needed to get the equations to work - I didn't know we have actually seen something like that.

It was never a "fudge factor" to make the equation of gravity "work". It was a prediction of the already extremely well-working equation. Not "Oh noes gravity is broken, we need 'dark matter' to fix it." Rather "Huh, gravity implies there is a mass here that we can't see with our electromagnetic detection devices".

Think of it this way. You're walking around a room blindfolded with a cane that has a pressure sensor on the end that uses a voice synthesizer to tell you the readings. You notice that all along a large flat plane the pressure sensor detects pressure equal to that with which you push. Newton's 3rd Law tells you that for this to happen, something must be pushing back with equal force. Something like a wall.

Now, do you say that the wall is a fudge to make Newton's 3rd Law work?Or do you say that Newton's 3rd Law implies that there is a wall there?

I mean you might as well say that the existence of the Sun is a fudge to make electromagnetic and gravitational equations work.

I'm not trying to rag on you or anything (I mean you said 'thank you' for evidence after all), just trying to clear up a misconception that I think has lead to a lot of unnecessary skepticism of dark matter.

Dark matter isn't just matter that isn't lit up (that was one of the original theories, but has since fallen to the wayside), it is matter that is fundamentally different and doesn't appear to interact with regular matter at all, except gravitationally.

it is matter that is fundamentally different and doesn't appear to interact with regular matter at all, except gravitationally.

More specifically, it doesn't appear to interact electromagnetically. Which just happens to exclude all of our direct detection methods (i.e. telescopes).

One candidate for dark matter is the neutralino, which is predicted by Supersymetric Theory and is basically a neutrino but heavier, and like a neutrino interacts through the Weak Interaction which allowed us to find neutrinos, and maybe even actual dark matter [arstechnica.com].

Weakly interacting does not mean that it interacts via the weak interaction.

That's right that is a possible English interpretation of "weakly", which is why what I quoted explicitly explained that the acronym "Weakly Interacting" came from their "expectation of the weak interaction" at the Electro-weak [wikipedia.org] scale, to make it clear they don't mean "weak interaction" as in "not very strong", but rather the Weak Force, one of the unified fundamental forces of the Standard Model.

Those observations actually *ARE* scientific evidence for dark matter. Unfortunately, they don't constrain what it could be very tightly. The current dark matter theory can shift to something else without changing it's name (and has in the past).

E.g., what is the temperature of the dark matter? For awhile there was argument between the hot dark matter interpretation and the cold dark matter interpretation...but both camps agreed it wasn't made of protons or neutrons and didn't radiate in the infrared.

Absolutely wrong. TFA even states this means nothing for dark matter, we knew that these galaxies were out there, we just hadn't spotted them yet. Besides, we've seen dark matter much closer to home. When galaxies collide, the gas pressure stops the regular matter, while the dark matter keeps moving along at the same speed. The dark matter has mass, so it creates a gravatic lens. We have seen these lenses, with no visible matter to create them, when galaxies collide.

That article gave me flashbacks on studying Boltzman distributions and the hydrogen atom. Strangely enough, if was only painful at first, I may have to go back review them.

"I'll note: this has nothing to do with dark matter. As it happens, 90% of the matter in the Universe is in a form that emits no light, but affects other matter through gravity. We know it exists... locally, in nearby galaxies and clusters of galaxies, too. This new result doesn't affect that, since the now un-hidden galaxies are very far away, like many billions of light years away. They can't possibly affect nearby galaxies, so they don't account for dark matter."

The Bad Astronomy post talks about dark matter:
[Note: before you ask, this has nothing to do with dark matter. See below!]
I’ll note: this has nothing to do with dark matter. As it happens, 90% of the matter in the Universe is in a form that emits no light, but affects other matter through gravity. We know it exists, and you can find out why here [discovermagazine.com]. We know it exists locally, in nearby galaxies and clusters of galaxies, too. This new result doesn’t affect that, since the now un-hidden galaxies

90% of the matter in the Universe is in a form that emits no light, but affects other matter through gravity.

Do we know for certain that the "dark matter" itself - whatever it proves to be - is actually in our universe? Is it possible that "dark matter" is just regular matter in some other universe(s) whose gravity is bleeding into our own?

No, its neither an assertion, nor a fact in the observational sense, it is a statement that is true by definition. If something can interact with things in our universe then it is in our universe, in the same sense that if you can add 1 to a number and get an integer, that number is also an integer.

The Visible Universe probably constitutes a very small (perhaps even infinitesimally small) fraction of the actual physical Universe. The rest will, according to Relativity, always be hidden.

Or it may be that the visible universe is smaller than the actual universe. This paper [arxiv.org] estimates the minimum possible diameter of the universe to be 24 gigaparsecs, which is four gigaparsecs less than the diameter of the observable universe. It's not likely, but if it were true it would mean we could look a billion lightyears in one direction and see a region of space, or we could look 77 billion lightyears in the opposite direction and see how that same region looked 76 billion years earlier, by seeing li

My first thought was, did they compensate for redshift? Apparently they did, the article didn't explain, but a commenter did:

30. TMB Says:
March 24th, 2010 at 7:02 pm
To everyone who's asking "why didn't they look at this before?" - it's a lot harder. In the rest frame, Lyman-alpha is in the far-UV and H-alpha (what physicists call Balmer-alpha) is in the optical. But out at these redshifts, Lyman-alpha is redshifted into the optical (which is easy to observe) and H-alpha is redshifted out into the infrared (which is harder to observe).

I'm guessing that this telescope in Chile only looks at the southern part of the sky. Does this mean that 90% of the universe is not visible to northern hemisphere telescopes?No, I didn't RTFA, this is Slasdot after all.

People are far too enamored with dark matter. It is extremely frustrating having to place everything in the context of dark matter (often with only the most tenuous connection) when trying to explain interesting observations to the general public. The author of this article, thankfully, made it clear at the top of the article that it was NOT related to dark matter and went on to explain the observation.

Pffftttt.... I didn't even bother reading the summary. Come to think of it, I don't think I looked at the headline either.

Er, but I'm guessing it was something to do with the seventh-generation iPhone. Anyway, whatever it was, I'm sure it'll be great- congratulations Steve, and all the Slashdotters dragging this thread offtopic rambling about astronomical nonsense should be ashamed of themselves.

Because estimates of the density of galaxies in the universe have been based on the volume that is closer to us and therefore relatively more visible, and did not suffer from the problem described. The assumption had been that the universe far away is, in a general manner, similar to the universe nearby, on the usual principle that there is nothing special about the place that we are. When the density of remote (and very early) galaxies fell off, it was assumed to be more likely to be an observational artef

"I’ll note: this has nothing to do with dark matter. As it happens, 90% of the matter in the Universe is in a form that emits no light, but affects other matter through gravity. We know it exists, and you can find out why here. We know it exists locally, in nearby galaxies and clusters of galaxies, too. This new result doesn’t affect that, since the now un-hidden galaxies are very far away, like many billions of light years away. They can’t possibly affect nearby galaxi

The missing mass is comprised of all the socks that have slipped through the spacetime continuum when you put them in the washing machine. They emit no radiation, but exert gravity. It's especially grave when you can't find a matching pair.

The socks don't escape through the washer. They escape through the dryer's lint trap. Eventually, after you've captured at least one socks-worth of lint, a sock somewhere in the world has to go "poof". (Note that it's not necessarily your sock, or your lint trap. It's a conservation-of-mass/quantum-lint-mechanics kind of thing.)

The lint that collects in your dryer is not made up of sock-matter. Dryer lint is mass created via the conversion of static electricity that accumulates while your dryer is running. If it weren't for the clever device to capture this energy and turn it into lint, running your dryer would cause an electrical discharge that makes a lightning bolt seem like a bee sting -- remember, E = mc^2.

The concundrum of missing socks remains unsolved, but the leading theory is that dark-matter socks spontaneously come into existence in your dryer, then meet your regular-matter socks, and puff out of existence with a corresponding release of a preposterous amount of energy (this, of course, is the source of energy that is converted into dryer-lint).

This theory is under fire, though, as a controlled study at the Institute for Laundering Science determined that socks sometimes disappear in the washer, not just the dryer -- explanation for what happens to the energy released in the dark/normal sock in the ashing cycle has not yet been determined.

Note also that this is why we wear dark socks to bed -- if we were to put them in the hamper with regular socks, the dark socks might come into contact with our light socks and explode.

The missing mass is comprised of all the socks that have slipped through the spacetime continuum when you put them in the washing machine. They emit no radiation, but exert gravity. It's especially grave when you can't find a matching pair.

I've always held to the 'Sock Fairy' theory. It explains both the missing sock, and how the nickle that you hear bouncing around in the dryer got there.

If this is the dark matter, then a lot of theories are going to need to be revised. There are good reasons why the dark matter was believed to be non-baryonic (i.e., without neutrons & protons). If this is the "missing matter", then the prevalence of helium vs. hydrogen needs a new explanation.

I'll note: this has nothing to do with dark matter. As it happens, 90% of the matter in the Universe is in a form that emits no light, but affects other matter through gravity. We know it exists, and you can find out why here. We know it exists locally, in nearby galaxies and clusters of galaxies, too. This new result doesn't affect that, since the now un-hidden galaxies are very far away, like many billions of light years away. They can't possibly affect nearby galaxies, so they don't account for dark matter.

Not really... there are problems at the galactic scale - when observing galaxies, the gravitational pull is just too high to be explained by normal matter alone (assuming everything else we know is mostly correct).

This has absolutely nothing do to with dark matter. So, yes it is a coincidence. And an approximation.

They're improving their technique for observing distant galaxies. Which doesn't in any way invalidate observations of (astronomically) very close galaxies. Which is what we base the existence of dark matter on.

[quote]Which doesn't in any way invalidate observations of (astronomically) very close galaxies. Which is what we base the existence of dark matter on.[/quote]Haven't heard that before, but I bet you're right. It's similar to the way programmes and media which try to explain quantum mechanics generally fail to even mention the "hidden variables" theory, and how that couldn't explain the theory.

Actually, it is just a coincidence. This has nothing to do with dark matter or dark energy.

This is an observation of distant galaxies. The theory of dark matter comes from observations much closer to home, within this galaxy. It's designed to explain why the galaxy doesn't fall apart; it has too little matter for gravity to do it on its own.

Since then, other independent observations have confirmed that galaxies have more matter than we can see.

... is the same figure used to justify the initial claims for dark matter.
Several initial sources claimed that there had to be abundant non-baryonic matter making up much of the universe, as otherwise, there would have to be about ten times as much normal matter as we were observing, and that, of course was absurd. So quite possibly this is so long to dark matter! Next question is, is there still any reason to postulate dark energy with the new values for average density and so on this will produce? Don't say goodbye to dark energy just yet, but expect some significant revisions.

Since only 10% of the universe is made up of baryons, that would make the other 90% bosons. Coincidence with the dark matter postings here?

The first argument for dark matter was based on the cosmological constant, as a property of the whole universe. Unless these galaxies are so far away they are outside the universe and don't contribute to whether the whole universe is gravitationally open or closed, they have just invalidated that argument, period. Localised observations show something about non-baryonic matter, but the arguments based on the Hubble constant and universal closure are behind much of our even looking for this stuff. The articl

I’ll note: this has nothing to do with dark matter. As it happens, 90% of the matter in the Universe is in a form that emits no light, but affects other matter through gravity. We know it exists, and you can find out why here. We know it exists locally, in nearby galaxies and clusters of galaxies, too. This new result doesn’t affect that, since the now un-hidden galaxies are very far away, like many billions of light years away. They can’t possibly affect nearby galaxies, so they don’t account for dark matter.

This will change the ratio of luminous matter:dark matter but not eliminate dark matter entirely.

Not that you said that it would necessarily get rid of dark matter, but it was a conclusion that suggested itself from the summary's wording.

It is imprecise to say physicists indicate there should be much more mass in the universe. What they say is that there is mass missing in every galaxy which implies it is missing from the universe but only on a galaxy by galaxy basis. Dark matter is necessary to explain why galaxies form. In other words the "missing" matter is in each and every galaxy. Discovering more galaxies doesn't affect that issue.

When I was a physics major in the dark ages they were just beginning to notice that computer simulations based on observed stellar quantities and masses had the annoying property of never resulting in galaxies. In subsequent years it was computed that the needed mass for galaxy formation wasn't off by a little but actually by a huge factor.

Eventually some observations of gravitational lensing have provided more evidence that there was huge amounts of mass measured in this indirect fashion that was simply not seen by exhaustive charting of the observed stars.